I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

[teslaman]

I installed a rebuilt powerhead about 5 years ago (thanks to help from this forum), and since that time the outboard has ran rather well. Over the past three years, the boat has only been out on the lake about 6 times I tried to start the motor over the winter, but couldn't get a spark. Today, I finally got around to troubleshooting the ingition system.

Result: No spark on all four cylinders. After performing some more tests, the key switch test resulted in a spark (validated using a spark tester with 1/2" gap).

Conclusion: Either the key switch is bad or the the key switch wire is shorted to ground somewhere on its way to the powerpack.

Question: Does the key switch fail often? Is it more likely that the wire is faulty? Am I missing something obvious? I ran out of time, so I didn't get a chance to troubleshoot further. The OMC part # is 0386947. I've seen keyswitches online from $16 to $62. Are the lower cost switches of adequate quality? Just looking for some advice from the experienced folks here before proceeding further.

Thanks

 

[Bosunsmate]

Re: I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

So i assume its turning over the motor?
What i do is i just pull out the control wiring plug and jump start it, if that fixes it then its the kill switch or the wires.
If not look for a ground elsewhere, the wires get hot near the cylinders if not strapped down away from there
I think the switches go more often but im sure many would say the opposite.
You can just unplug the grounding wire in the keyswitch and see if that fixes it before buying the switch which would show it was a ground back in the wiring

 

[Lone Duck]

Re: I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

Get a test light and clip to ground then touch batt terminal, if it lights ,turn on key, touch that terminal if it lights your problem is in the wire to engine. So test that wire with the key on where it connects to engine it might be the plug in is corroded.

 

[emdsapmgr]

Re: I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

OMC key switches are pretty high quality. Usually last for many years. If yours is original, it may finally be getting to the end of it's normal lifespan, so it's not unusual to have to replace it. If the key switch is ever exposed to the weather (rain, snow) that will tend to shorten it's life. I'd only replace the switch with the current factory one (508180), to get the best quality. Probably the more expensive switch.

 

[glenn property of pam]

Re: I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

if you have a lanyard kill switch start by pulling the wires of that first as there cheap and tend to crack.

 

[teslaman]

Re: I think I need a new key switch for my 73 115 hp Johnson (4 cylinders)

Lone Duck,

Thanks for next troubleshooting steps. I plan on testing the keyswitch and wire to the engine this weekend.
I have two clarification questions regarding the troubleshooting instructions that you provided:

"Get a test light and clip to ground then touch batt terminal,..." - (Is this to verify that the test light works by connetcting it directly to the battery?)

"...if it lights, turn on key, touch that terminal..." - Which terminal are you refering to?

Thanks for your help